Skip to content

Commit

Permalink
lockdep: Fix lockdep recursion
Browse files Browse the repository at this point in the history 
Steve reported that lockdep_assert*irq*(), when nested inside lockdep
itself, will trigger a false-positive.

One example is the stack-trace code, as called from inside lockdep,
triggering tracing, which in turn calls RCU, which then uses
lockdep_assert_irqs_disabled().

Fixes: a21ee60 ("lockdep: Change hardirq{s_enabled,_context} to per-cpu variables")
Reported-by: Steven Rostedt <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
  • Loading branch information
Peter Zijlstra authored and Ingo Molnar committed Oct 9, 2020
1 parent 2bb8945 commit 4d00409
Show file tree
Hide file tree
Showing 2 changed files with 67 additions and 45 deletions.
13 changes: 8 additions & 5 deletions include/linux/lockdep.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -534,6 +534,7 @@ do { \

DECLARE_PER_CPU(int, hardirqs_enabled);
DECLARE_PER_CPU(int, hardirq_context);
DECLARE_PER_CPU(unsigned int, lockdep_recursion);

/*
* The below lockdep_assert_*() macros use raw_cpu_read() to access the above
Expand All @@ -543,33 +544,35 @@ DECLARE_PER_CPU(int, hardirq_context);
* read the value from our previous CPU.
*/

#define __lockdep_enabled (debug_locks && !raw_cpu_read(lockdep_recursion))

#define lockdep_assert_irqs_enabled() \
do { \
WARN_ON_ONCE(debug_locks && !raw_cpu_read(hardirqs_enabled)); \
WARN_ON_ONCE(__lockdep_enabled && !raw_cpu_read(hardirqs_enabled)); \
} while (0)

#define lockdep_assert_irqs_disabled() \
do { \
WARN_ON_ONCE(debug_locks && raw_cpu_read(hardirqs_enabled)); \
WARN_ON_ONCE(__lockdep_enabled && raw_cpu_read(hardirqs_enabled)); \
} while (0)

#define lockdep_assert_in_irq() \
do { \
WARN_ON_ONCE(debug_locks && !raw_cpu_read(hardirq_context)); \
WARN_ON_ONCE(__lockdep_enabled && !raw_cpu_read(hardirq_context)); \
} while (0)

#define lockdep_assert_preemption_enabled() \
do { \
WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT) && \
debug_locks && \
__lockdep_enabled && \
(preempt_count() != 0 || \
!raw_cpu_read(hardirqs_enabled))); \
} while (0)

#define lockdep_assert_preemption_disabled() \
do { \
WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT) && \
debug_locks && \
__lockdep_enabled && \
(preempt_count() == 0 && \
raw_cpu_read(hardirqs_enabled))); \
} while (0)
Expand Down
99 changes: 59 additions & 40 deletions kernel/locking/lockdep.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -76,6 +76,23 @@ module_param(lock_stat, int, 0644);
#define lock_stat 0
#endif

DEFINE_PER_CPU(unsigned int, lockdep_recursion);
EXPORT_PER_CPU_SYMBOL_GPL(lockdep_recursion);

static inline bool lockdep_enabled(void)
{
if (!debug_locks)
return false;

if (raw_cpu_read(lockdep_recursion))
return false;

if (current->lockdep_recursion)
return false;

return true;
}

/*
* lockdep_lock: protects the lockdep graph, the hashes and the
* class/list/hash allocators.
Expand All @@ -93,15 +110,15 @@ static inline void lockdep_lock(void)

arch_spin_lock(&__lock);
__owner = current;
current->lockdep_recursion++;
__this_cpu_inc(lockdep_recursion);
}

static inline void lockdep_unlock(void)
{
if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current))
return;

current->lockdep_recursion--;
__this_cpu_dec(lockdep_recursion);
__owner = NULL;
arch_spin_unlock(&__lock);
}
Expand Down Expand Up @@ -393,10 +410,15 @@ void lockdep_init_task(struct task_struct *task)
task->lockdep_recursion = 0;
}

static __always_inline void lockdep_recursion_inc(void)
{
__this_cpu_inc(lockdep_recursion);
}

static __always_inline void lockdep_recursion_finish(void)
{
if (WARN_ON_ONCE((--current->lockdep_recursion) & LOCKDEP_RECURSION_MASK))
current->lockdep_recursion = 0;
if (WARN_ON_ONCE(__this_cpu_dec_return(lockdep_recursion)))
__this_cpu_write(lockdep_recursion, 0);
}

void lockdep_set_selftest_task(struct task_struct *task)
Expand Down Expand Up @@ -3659,7 +3681,7 @@ void lockdep_hardirqs_on_prepare(unsigned long ip)
if (unlikely(in_nmi()))
return;

if (unlikely(current->lockdep_recursion & LOCKDEP_RECURSION_MASK))
if (unlikely(__this_cpu_read(lockdep_recursion)))
return;

if (unlikely(lockdep_hardirqs_enabled())) {
Expand Down Expand Up @@ -3695,7 +3717,7 @@ void lockdep_hardirqs_on_prepare(unsigned long ip)

current->hardirq_chain_key = current->curr_chain_key;

current->lockdep_recursion++;
lockdep_recursion_inc();
__trace_hardirqs_on_caller();
lockdep_recursion_finish();
}
Expand Down Expand Up @@ -3728,7 +3750,7 @@ void noinstr lockdep_hardirqs_on(unsigned long ip)
goto skip_checks;
}

if (unlikely(current->lockdep_recursion & LOCKDEP_RECURSION_MASK))
if (unlikely(__this_cpu_read(lockdep_recursion)))
return;

if (lockdep_hardirqs_enabled()) {
Expand Down Expand Up @@ -3781,7 +3803,7 @@ void noinstr lockdep_hardirqs_off(unsigned long ip)
if (in_nmi()) {
if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
return;
} else if (current->lockdep_recursion & LOCKDEP_RECURSION_MASK)
} else if (__this_cpu_read(lockdep_recursion))
return;

/*
Expand Down Expand Up @@ -3814,7 +3836,7 @@ void lockdep_softirqs_on(unsigned long ip)
{
struct irqtrace_events *trace = &current->irqtrace;

if (unlikely(!debug_locks || current->lockdep_recursion))
if (unlikely(!lockdep_enabled()))
return;

/*
Expand All @@ -3829,7 +3851,7 @@ void lockdep_softirqs_on(unsigned long ip)
return;
}

current->lockdep_recursion++;
lockdep_recursion_inc();
/*
* We'll do an OFF -> ON transition:
*/
Expand All @@ -3852,7 +3874,7 @@ void lockdep_softirqs_on(unsigned long ip)
*/
void lockdep_softirqs_off(unsigned long ip)
{
if (unlikely(!debug_locks || current->lockdep_recursion))
if (unlikely(!lockdep_enabled()))
return;

/*
Expand Down Expand Up @@ -4233,11 +4255,11 @@ void lockdep_init_map_waits(struct lockdep_map *lock, const char *name,
if (subclass) {
unsigned long flags;

if (DEBUG_LOCKS_WARN_ON(current->lockdep_recursion))
if (DEBUG_LOCKS_WARN_ON(!lockdep_enabled()))
return;

raw_local_irq_save(flags);
current->lockdep_recursion++;
lockdep_recursion_inc();
register_lock_class(lock, subclass, 1);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
Expand Down Expand Up @@ -4920,11 +4942,11 @@ void lock_set_class(struct lockdep_map *lock, const char *name,
{
unsigned long flags;

if (unlikely(current->lockdep_recursion))
if (unlikely(!lockdep_enabled()))
return;

raw_local_irq_save(flags);
current->lockdep_recursion++;
lockdep_recursion_inc();
check_flags(flags);
if (__lock_set_class(lock, name, key, subclass, ip))
check_chain_key(current);
Expand All @@ -4937,11 +4959,11 @@ void lock_downgrade(struct lockdep_map *lock, unsigned long ip)
{
unsigned long flags;

if (unlikely(current->lockdep_recursion))
if (unlikely(!lockdep_enabled()))
return;

raw_local_irq_save(flags);
current->lockdep_recursion++;
lockdep_recursion_inc();
check_flags(flags);
if (__lock_downgrade(lock, ip))
check_chain_key(current);
Expand Down Expand Up @@ -4979,7 +5001,7 @@ static void verify_lock_unused(struct lockdep_map *lock, struct held_lock *hlock

static bool lockdep_nmi(void)
{
if (current->lockdep_recursion & LOCKDEP_RECURSION_MASK)
if (raw_cpu_read(lockdep_recursion))
return false;

if (!in_nmi())
Expand All @@ -5000,7 +5022,10 @@ void lock_acquire(struct lockdep_map *lock, unsigned int subclass,

trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);

if (unlikely(current->lockdep_recursion)) {
if (!debug_locks)
return;

if (unlikely(!lockdep_enabled())) {
/* XXX allow trylock from NMI ?!? */
if (lockdep_nmi() && !trylock) {
struct held_lock hlock;
Expand All @@ -5023,7 +5048,7 @@ void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
raw_local_irq_save(flags);
check_flags(flags);

current->lockdep_recursion++;
lockdep_recursion_inc();
__lock_acquire(lock, subclass, trylock, read, check,
irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
lockdep_recursion_finish();
Expand All @@ -5037,13 +5062,13 @@ void lock_release(struct lockdep_map *lock, unsigned long ip)

trace_lock_release(lock, ip);

if (unlikely(current->lockdep_recursion))
if (unlikely(!lockdep_enabled()))
return;

raw_local_irq_save(flags);
check_flags(flags);

current->lockdep_recursion++;
lockdep_recursion_inc();
if (__lock_release(lock, ip))
check_chain_key(current);
lockdep_recursion_finish();
Expand All @@ -5056,13 +5081,13 @@ noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
unsigned long flags;
int ret = 0;

if (unlikely(current->lockdep_recursion))
if (unlikely(!lockdep_enabled()))
return 1; /* avoid false negative lockdep_assert_held() */

raw_local_irq_save(flags);
check_flags(flags);

current->lockdep_recursion++;
lockdep_recursion_inc();
ret = __lock_is_held(lock, read);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
Expand All @@ -5077,13 +5102,13 @@ struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
struct pin_cookie cookie = NIL_COOKIE;
unsigned long flags;

if (unlikely(current->lockdep_recursion))
if (unlikely(!lockdep_enabled()))
return cookie;

raw_local_irq_save(flags);
check_flags(flags);

current->lockdep_recursion++;
lockdep_recursion_inc();
cookie = __lock_pin_lock(lock);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
Expand All @@ -5096,13 +5121,13 @@ void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
{
unsigned long flags;

if (unlikely(current->lockdep_recursion))
if (unlikely(!lockdep_enabled()))
return;

raw_local_irq_save(flags);
check_flags(flags);

current->lockdep_recursion++;
lockdep_recursion_inc();
__lock_repin_lock(lock, cookie);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
Expand All @@ -5113,13 +5138,13 @@ void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
{
unsigned long flags;

if (unlikely(current->lockdep_recursion))
if (unlikely(!lockdep_enabled()))
return;

raw_local_irq_save(flags);
check_flags(flags);

current->lockdep_recursion++;
lockdep_recursion_inc();
__lock_unpin_lock(lock, cookie);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
Expand Down Expand Up @@ -5249,15 +5274,12 @@ void lock_contended(struct lockdep_map *lock, unsigned long ip)

trace_lock_acquired(lock, ip);

if (unlikely(!lock_stat || !debug_locks))
return;

if (unlikely(current->lockdep_recursion))
if (unlikely(!lock_stat || !lockdep_enabled()))
return;

raw_local_irq_save(flags);
check_flags(flags);
current->lockdep_recursion++;
lockdep_recursion_inc();
__lock_contended(lock, ip);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
Expand All @@ -5270,15 +5292,12 @@ void lock_acquired(struct lockdep_map *lock, unsigned long ip)

trace_lock_contended(lock, ip);

if (unlikely(!lock_stat || !debug_locks))
return;

if (unlikely(current->lockdep_recursion))
if (unlikely(!lock_stat || !lockdep_enabled()))
return;

raw_local_irq_save(flags);
check_flags(flags);
current->lockdep_recursion++;
lockdep_recursion_inc();
__lock_acquired(lock, ip);
lockdep_recursion_finish();
raw_local_irq_restore(flags);
Expand Down

0 comments on commit 4d00409

Please sign in to comment.